In March 1999 a new law prohibiting driving while impaired by illegal drugs was introduced in Belgium. The legal procedure consists of a) a field impairment test, b) a urine immunoassay for 4 drug groups and c) ultimate proof by plasma analysis (GC-MS with fixed cut-offs). Over about two years the analysis of 896 blood samples revealed the presence of illicit drug(s) above cut-off in 85% of the cases. For the 15% "false positives" (failed impairment test and positive urine assay without confirmation in plasma) we investigated the possible reasons for impaired behavior. The presence of alcohol and psychoactive medication stands for an important number of our 'false positives'. The results adduce arguments for introducing psychotropic medicines in our traffic law. Our findings further suggest that false positive cases can be reduced by minimizing the delay before blood sampling and optimizing sample preservation. Harmonization of the strategy for detection and penalization of impaired drivers (alcohol and/or drugs) is highly recommended. (Author/publisher) For the covering abstract of the conference see ITRD Abstract No. E201067.
Samenvatting